Browsing by Author "Curro, N. J."

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Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic Resonance
(2010-10-01)
Grafe, H. -J.
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Curro, N. J.
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Young, B. L.
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Vyalikh, A.
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Vavilova, J.
We report detailed O-17, La-139, and Cu-63,Cu-65 Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La1.875Ba0.125CuO4 single crystal and in oriented powder samples of La1.8-x Eu0.2Sr (x) CuO4. We observe a partial wipeout of the O-17 NMR intensity and a simultaneous drop of the O-17 electric field gradient (EFG) at low temperatures where the spin stripe order sets in. In contrast, the Cu-63,Cu-65 intensity is completely wiped out at the same temperature. The drop of the O-17 quadrupole frequency is compatible with a charge stripe order. The O-17 spin lattice relaxation rate shows a peak similar to that of the La-139, which is of magnetic origin. This peak is doping dependent and is maximal at x a parts per thousand 1/8.
Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic Resonance
(2010-10-01)
Grafe, H. -J.
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Curro, N. J.
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Young, B. L.
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Vyalikh, A.
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Vavilova, J.
We report detailed (17)O, (139)La, and (63,65)Cu Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La(1.875)Ba(0.125)CuO(4) single crystal and in oriented powder samples of La(1.8-x) Eu(0.2)Sr (x) CuO(4). We observe a partial wipeout of the (17)O NMR intensity and a simultaneous drop of the (17)O electric field gradient (EFG) at low temperatures where the spin stripe order sets in. In contrast, the (63,65)Cu intensity is completely wiped out at the same temperature. The drop of the (17)O quadrupole frequency is compatible with a charge stripe order. The (17)O spin lattice relaxation rate shows a peak similar to that of the (139)La, which is of magnetic origin. This peak is doping dependent and is maximal at x a parts per thousand 1/8.
Coexistence of antiferromagnetism and superconductivity in CeCo(In0.9Cd0.1)(5): A spin lattice relaxation study
(2008-04-01)
Urbano, R. R.
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Young, B. -L.
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Curro, N. J.
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Thompson, J. D.
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Pham, L. D.
We present an In(1) NQR study on the heavy-fermion (HF) compound CeCo(In1-xCdx)(5) (x = 0.10). Bulk measurements indicate that Cd doping acts as an electronic tuning agent in CeCoIn5, and that superconductivity (SC) and antiferromagnetism (AFM) may coexist at ambient pressure for 0.05 < x < 0.15. For x = 0.10, the nuclear spin lattice relaxation rate shows a broad peak at the Neel temperature T-N = 2.8 K, with a subsequent onset of SC at T-c similar or equal to 1.2 K. Our results provide strong evidence for microscopic coexistence of these two ground states. The nuclear magnetization recovery curves in both the ordered and mixed states reveal a single T-i-component, which suggests a homogeneous nature of the Ce-4f(1) electronic state. (c) 2007 Elsevier B.V. All rights reserved.
Interacting antiferromagnetic droplets in quantum critical CeCoIn5
(2007-10-05)
Urbano, R. R.
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Young, B.-L.
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Curro, N. J.
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Thompson, J. D.
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Pham, L. D.
The heavy fermion superconductor CeCoIn5 can be tuned between superconducting and antiferromagnetic ground states by hole doping with Cd. Nuclear magnetic resonance data indicate that these two orders coexist microscopically with an ordered moment similar to 0.7 mu(B). As the ground state evolves, there is no change in the low-frequency spin dynamics in the disordered state. These results suggest that the magnetism emerges locally in the vicinity of the Cd dopants.
Microscopic evidence for field-induced magnetism in CeCoIn5
(2007-01-19)
Young, B. -L.
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Urbano, R. R.
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Curro, N. J.
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Thompson, J. D.
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Sarrao, J. L.
We present NMR data in the normal and superconducting states of CeCoIn5 for fields close to H-c2(0)=11.8 T in the ab plane. Recent experiments identified a first-order transition from the normal to superconducting state for H > 10.5 T, and a new thermodynamic phase below 290 mK within the superconducting state. We find that the Knight shifts of the In(1), In(2), and the Co are discontinuous across the first-order transition and the magnetic linewidths increase dramatically. The broadening differs for the three sites, unlike the expectation for an Abrikosov vortex lattice, and suggests the presence of static spin moments in the vortex cores. In the low-temperature and high-field phase, the broad NMR lineshapes suggest ordered local moments, rather than a long-wavelength quasiparticle spin density modulation expected for an FFLO phase.
Probing the magnetism in the CeMIn5 heavy fermion systems by NMR
(2008-04-01)
Curro, N. J.
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Urbano, R. R.
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Young, B. -L.
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電子物理學系
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Department of Electrophysics
The CeMIn5 heavy fermion system exhibits antiferromagnetism for both M = Rh and M = Co. CeRhIn5 is antiferromagnetic at ambient pressure and superconducting under hydrostatic pressure, whereas CeCoIn5 is superconducting at ambient pressure, but becomes antiferromagnetic with substitution of In by a few percent of Cd. Pure CeCoIn5 exhibits a field-induced magnetic phase that coexists with the superconductivity. Nuclear magnetic resonance (NMR) and nuclear quadrupolar resonance (NQR) studies of the In(1), In(2) and Co sites reveal similar features in the magnetic states of these systems. (c) 2007 Published by Elsevier B.V.